1. Field of the Invention
This invention relates to a liquid mixing ratio sensor which optically detects mixing ratio of a mixing liquid which includes at least two kinds of liquid components.
2. Description of Prior Art
Electrolyte solution of a battery cell decreases its specific gravity with the development of discharge. The specific gravity and the refraction index are in proportion each other, so that measurement of the refraction index leads to detecting the condition of the battery cell.
These types of sensors have been introduced in Japanese Patent Publication No. 56-37498 and Japanese provisional publication Patent No. 57-84337.
In the Japanese Patent Publication No. 56-37498, a sensor is provided which has a light source 100, a light sensitive element 110 and a light reflection mirror 170 as seen in FIG. 4. Incident light beams 120 and reflection light beams 130 have incident angle toward an optical axis.
The incident angle is determined to be less than a light critical angle which is formed from a transparent material 160 consisting a glass 150 and a transparent synthetic material 140 toward a liquid.
In the Japanese provisional publication Patent No. 57-84337, there are provided a sensor comprising a triangular prism 210, a trapezoid prism 220 disposed in the liquid to be detected, first light source 230, second light source 240, first optoelectronic transducer 250 and second optoelectronic transducer 260, a calculator 270 which is electrically connected to the first and second transducers 250, 260 and a displa device 280a as seen in FIG. 5.
However, the transparent material of the former has -1.times.10.sup.-6 /.degree. C. at its thermal coefficient of refraction index, while thermal coefficient of refraction index of the mixing liquid to be detected is -2.times.10.sup.-4 /.degree. C..about.-6.times.10.sup.-4 /.degree. C. Change of the ambient temperature causes to variation of the critical angle so as to produce error in measurement values.
The latter has two prisms which makes all the structure great in dimension, and required to do complicated calculations to compensate for temperature.
Therefore, the invention has its object to provide a mixing liquid ratio sensor which is capable of eliminating all the drawbacks mentioned above, enabling to provide a mixing liquid ratio sensor which detects mixing ratio with high precision, low cost and simple construction.
According to the invention there is provided a liquid mixing ratio sensor which includes a boundary in which a transparent plate contacts at one end with a mixing liquid of at least two kinds of liquid components, and having a light emitting element, a light receiving element which detects a mixing ratio of the mixing liquid by a change of light reflection from the boundary;
the sensor comprising; PA1 the transparent plate making other end contact with a gel-like transparent material to serve as a reference boundary, a refraction index of the gel-like transparent material being identical to that of the mixing liquid at desired the mixing ratio to be detected; PA1 the light emitting element having a reflection side, and the light emitting element and the reflection side being located to oppose to a wall perpendicular to both ends of the transparent material, the reflection side being placed such as to reflect light beams reflected from the boundary toward the reference boundary; PA1 a light screen placed at the transparent plate to prevent the light beams from entering the reflection side, the light beams being ones which does not reflect from the boundary; PA1 the light receiving element being located such that the light beams from the light emitting element reflects from the boundary, the reflection side, and refracted at the reference plate to fall on the light receiving element when the refraction index of the mixing liquid to be detected is less than that of the gel-like transparent material.
These and other objects and advantages of the invention will be apparent upon reference to the following specification, attendant claims, and drawings.